This line was either commented out, or uncommented, to switch tor on or off.

Observed behavior: When commented out (tor turned off), clicking on
the hidden discussions first displays the "initial burst" that appears
to have come in the original web page, and after about one second, the
rest of the article and article header appear, downloaded on demand
from slashdot.

When enabled, the next (first) one also appears. After that, no more
will download.

When disabled again, there will be one more "does not appear". After
that, they will all appear.

The delay of one between enabling/disabling, and actual, I'm guessing
to be privoxy noticing a change to its config file.